What makes a good Irish Catholic boy spend six years researching and writing a book on a scrappy Jewish kid from South Philadelphia?

When Tim Kelly was growing up in Collingswood, N.J., he loved basketball — but the avid player on Catholic Youth Organization squads admits he wasn’t good enough to make his high school team. Maybe that’s why he found a kindred spirit in Louis “Red” Klotz, who never topped 5-foot-7 but overcame his diminutive size, anti-Semitism and much more to succeed in basketball.

Klotz did all that — and also became an ambassador for America and the Jewish people — despite earning the title of “losing-est” player ever during his storied career with the Washington Generals, who toured the world as the competing exhibition team for the Harlem Globetrotters.

Kelly, who now lives in Ocean City, N.J., interviewed the nonagenarian as well as his family and friends for a newly published 300-page tome, The Legend of Red Klotz: How Basketball’s Loss Leader Won Over the World — 14,000 Times.

Klotz, former owner-player-coach of the Generals, lost those 14,000 games to the Globetrotters — although he launched a long, two-hand set shot allowing his team to beat the famed exhibition team in 1971, when he was nearly 50. The energetic red-haired point guard — the shortest player to win an NBA championship, in 1948 with the Baltimore Bullets — played with the Generals well into his 60s. His number 3 was retired in 2009.

“Red Klotz never complained about anything. He just kept on going,” said Kelly, 62, a former newspaper writer and editor who recently retired from his job as director of public relations at The Richard Stockton College of New Jersey.

“When I met Red at a Harlem Globetrotters game at Stockton, I knew exactly who he was. I was a big fan,” Kelly said. “I always seemed to gravitate to the Generals. I favored the underdog.”

Klotz, 92, relocated to Atlantic City — hometown of his wife of 72 years, Gloria — years ago, and now lives in Margate, N.J.

“He’s got integrity, he’s funny, he’s smart. Despite his 14,000 losses, he’s a winner,” said Kelly, who bonded with Klotz and considers him a second father. “It’s partly generational, being one of the'greatest generation' that lived through the Great Depression and World War II. They just have a different mindset."

Growing up Jewish in the first half of the 20th century and having to deal with anti-Semitism from a young age certainly helped mold that mindset.

“Red's long odds in making it as a basketball player were not enhanced by the prejudice Jews of that era endured,” Kelly said.

Born in 1921 to Russian-Jewish immigrants, Klotz first made a name for himself on the basketball court at South Philadelphia High School. A member of the 1939-40 Philadelphia city champion high school team, he was initially recruited by the late Temple University Owls’ Coach Jimmy Usilton. But it was thought that Temple had a quota on Jewish basketball players, and Mendy Snyder was already on the varsity team.

“The common belief was that Temple wanted Snyder to graduate before the Owls unveiled a 5-foot-7 guard who would dominate possession of the basketball,” Kelly wrote.

But Klotz didn’t flinch; then-Villanova College coach Al Severance was happy to have him play at the Catholic institution on the Main Line. Klotz led the team to a spectacular winning season. He was back for more in 1941, but war intervened after that. Instead of returning for a third season, Klotz was serving in the Army and had turned pro, to boot.

He joined the South Philadelphia Hebrew Association team, known as the SPHAS — who defeated the Trotters in Klotz’s first game against them.

“When Red played for the SPHAS, half the crowd was Jewish and half anti-Semite,” Kelly recalled. “There was a ‘lady’ who sat in the front row and would jump out of her seat to jab the players in their legs with her hatpin as they ran past.”

Klotz didn’t let it get to him. After playing for the SPHAS, he spent that 1948 championship season with the Baltimore Bullets.

In 1952, at the behest of Globetrotters’ founder Abe Saperstein, Klotz created the Generals to be the main competition for the Trotters on their national and international tours. As a Jew, Klotz was able to identify with the talented young black men who also endured racism and were sometimes treated better off the court on their trips abroad than in some parts of their own country.

Saperstein, SPHAS’ owner Eddie Gottlieb and other Jewish sports entrepreneurs who helped pave the way for today’s pro basketball industry, plus additional Philadelphia Jewish athletes who contributed to the game, also get plenty of ink in Kelly’s homage. It’s enough to make any hoops enthusiast kvell, but it always comes back to Klotz and his longevity.

As a world traveler who played throughout Europe, South America, Australia and the Middle East, Klotz became an ambassador for the game and also for diversity.

“He was able to combat the propaganda out there about America. It’s a role that he has cherished and taken very seriously,” Kelly said.

During a 1953 visit to Egypt, Saperstein and his team met with the nation’s first president, Mohammed Naguib.

Klotz recalled the experience for Kelly's book: “I reminded him that fighting has been going on for thousands of years and I asked him if he could do his part to make peace. He looked at me and said, ‘Be patient.’ ”

Naguib lost power to Gamal Abdel Nasser the following year. “Sixty years later, we still aren’t close to (Middle East) peace! Be patient, my eye," Klotz recounted.

In Heidelberg, where the teams played in venues in which Hitler had delivered some of his most notorious speeches during the Third Reich, Klotz sensed the irony.

“Here was a team of very talented black ballplayers, coached by a Jewish guy, playing against a bunch of white guys of every nationality,” he told Kelly. “It was the idea of the American melting pot on display in postwar Germany, on a stage previously commanded by Hitler. We were showing the world that the American ideal of working and playing together can actually succeed.”

Although there have been several books and documentaries that have examined facets of Klotz’s career, Kelly’s is the first comprehensive biography about his life and times – and the first project on which he fully collaborated, said Klotz’s oldest daughter, Ronee Groff.

“It’s fun to have somebody tell your stories that span history,” said Groff, who resides in Egg Harbor Township, N.J. “It‘s been emotional and exciting for Dad.”

Klotz, who recently had a stroke that has impaired his speech, wanted to impart the lessons of sport through the biography, and believes it has achieved that goal, his daughter said.

“Knowing that the world would see basketball through his eyes, and learn about the Globetrotter and Generals tours that allowed the teams to represent America — it’s meant so much to him,” Groff said.

Tim Kelly will speak about the life and times of Red Klotz at a luncheon sponsored by The Markward Memorial Basketball Club at 2:30 p.m. on March 19 at Cannstatter, 9130 Academy Rd., Philadelphia. The luncheon costs $20 and is open to the public. For more information, contact (215) 360-7144. Kelly’s book is available on amazon.com.